Add DPI scale factor to the render root state

masonry/src/app/render_root.rs

@@ -64,11 +64,6 @@ pub struct RenderRoot {
     /// Current size of the window.
     pub(crate) size: PhysicalSize<u32>,
 
-    /// DPI scale factor.
-    ///
-    /// Kurbo coordinates are assumed to be in logical pixels
-    pub(crate) scale_factor: f64,
-
     /// Is `Some` if the most recently displayed frame was an animation frame.
     pub(crate) last_anim: Option<Instant>,
 
@@ -147,6 +142,11 @@ pub(crate) struct RenderRootState {
     /// Pass tracing configuration, used to skip tracing to limit overhead.
     pub(crate) trace: PassTracing,
     pub(crate) inspector_state: InspectorState,
+
+    /// DPI scale factor.
+    ///
+    /// Kurbo coordinates are assumed to be in logical pixels
+    pub(crate) scale_factor: f64,
 }
 
 pub(crate) struct MutateCallback {
@@ -258,7 +258,6 @@ impl RenderRoot {
             root: WidgetPod::new(root_widget).erased(),
             size_policy,
             size: PhysicalSize::new(0, 0),
-            scale_factor,
             last_anim: None,
             last_mouse_pos: None,
             global_state: RenderRootState {
@@ -290,6 +289,7 @@ impl RenderRoot {
                     is_picking_widget: false,
                     hovered_widget: None,
                 },
+                scale_factor,
             },
             widget_arena: WidgetArena {
                 widgets: TreeArena::new(),
@@ -338,7 +338,7 @@ impl RenderRoot {
     pub fn handle_window_event(&mut self, event: WindowEvent) -> Handled {
         match event {
             WindowEvent::Rescale(scale_factor) => {
-                self.scale_factor = scale_factor;
+                self.global_state.scale_factor = scale_factor;
                 self.request_render_all();
                 Handled::Yes
             }
@@ -443,7 +443,7 @@ impl RenderRoot {
 
         // TODO - Handle invalidation regions
         let scene = run_paint_pass(self);
-        let tree_update = run_accessibility_pass(self, self.scale_factor);
+        let tree_update = run_accessibility_pass(self, self.global_state.scale_factor);
         (scene, tree_update)
     }
 
@@ -539,7 +539,7 @@ impl RenderRoot {
     }
 
     pub(crate) fn get_kurbo_size(&self) -> kurbo::Size {
-        let size = self.size.to_logical(self.scale_factor);
+        let size = self.size.to_logical(self.global_state.scale_factor);
         kurbo::Size::new(size.width, size.height)
     }
 

masonry/src/core/contexts.rs

@@ -780,6 +780,22 @@ impl_context_method!(
     }
 );
 
+impl_context_method!(PaintCtx<'_>, AccessCtx<'_>, {
+    /// Get DPI scaling factor.
+    ///
+    /// This is not required for most widgets, and should be used only for precise
+    /// rendering, such as rendering single pixel lines or selecting image variants.
+    /// This is currently only provided in the render stages, as these are the only passes which
+    /// are re-run when the scale factor changes.
+    ///
+    /// Note that accessibility nodes and paint results will automatically be scaled by Masonry.
+    /// This also doesn't account for the widget's current transform, which cannot currently be
+    /// accessed by widgets directly.
+    pub fn get_scale_factor(&self) -> f64 {
+        self.global_state.scale_factor
+    }
+});
+
 // Methods on all context types
 // Access status information (hovered/pointer captured/disabled/etc).
 impl_context_method!(

masonry/src/passes/layout.rs

@@ -217,7 +217,8 @@ pub(crate) fn run_layout_pass(root: &mut RenderRoot) {
     ctx.place_child(&mut root.root, Point::ORIGIN);
 
     if let WindowSizePolicy::Content = root.size_policy {
-        let new_size = LogicalSize::new(size.width, size.height).to_physical(root.scale_factor);
+        let new_size =
+            LogicalSize::new(size.width, size.height).to_physical(root.global_state.scale_factor);
         if root.size != new_size {
             root.size = new_size;
             root.global_state